The present invention relates generally to circuit condition monitoring devices for use in electrical power distribution systems, and in particular to a clamp mechanism and housing for mounting such devices to the various sized cables of such distribution systems.
Electrical power distribution systems may require the use of a variety of circuit condition monitoring devices to facilitate the detection and location of system malfunctions. Such devices include manually and automatically reset current fault indicators, such as those manufactured by E.O. Schweitzer Manufacturing Co., and described in U.S. Pat. Nos. 4,288,743, 4,086,529 and 3,676,740 of the present inventor, as well as voltage monitoring devices, such as described in U.S. Pat. Nos. 4,251,770, 4,152,643, 4,263,350 and U.S. Pat. No. 4,550,288 of the present inventor. The devices may be either of the test point mounted type for mounting on a system test point, or of the clamp-on type, for clamping directly onto a cable of the system.
Clamp on type devices typically include a housing containing a clamp mechanism affixed to the housing for mounting the housing on the cable. Frequently, the clamp mechanism serves the additional function of establishing either magnetic or electrostatic communication, or both, between the electrical conductor in the cable and appropriate sensing components of the monitoring apparatus. Since power cables used in the industry are routinely of various diameters, it is necessary that the clamping mechanism accommodate a range of cable diameters.
In one prior clamp mechanism, which is described in U.S. Pat. No. 4,456,873 of the present inventor, a plurality of flexible metallic strips are combined to form a generally square-shaped magnetic core for use with a circuit condition monitoring device. One end of the core is affixed to the device housing, and the opposite end is detachably received within an aperture in the housing opposite the first end. In use, the free end of the core is displaced from the device housing, allowing the core to be passed around a cable. The free end is then inserted in the aperture to lock the device to the cable. Although this disclosure allows the installer of the device to virtually mount it at any place along the length of the cable, the installer must use two hands to accomplish this task. Also, such a device may not be suitable when mounting to a large range of cable diameters.
In another prior clamp mechanism described in U.S. Pat. No. 4,646,006 two inwardly biased wire clamps are pre-configured to a spaced-apart condition by a spring under compression prior to receiving the cable. The mechanism is maneuvered with a single hotstick so that the cable deforms the pre-configured spring to cause the clamp to engage the cable. Although this device allows one handed mounting via a hotstick, the biased wire clamps are prone to weaken and thus slip and effect any desired monitoring of the cable. Also, disengagement of such a device requires a force large enough to open the biased wire clamps which becomes difficult when the installer is on a ladder or the like; further, this force may damage the device or cable.
The present invention is directed to a clamping mechanism and housing whereby a monitoring device can be installed on a wide range of electrical cable diameters using a single lineman's hotstick. The device is maneuvered with the hotstick to a desired location on a cable and mounted thereto. The hotstick is then used to clamp the device securely onto a wide range of cable diameters. The one-hand installation provides for the monitoring of varying diameter cables at more diverse locations as well as contributing to safety, particularly where it is necessary for the lineman to ascent a ladder in order to install the device, or where the monitored cable is closely spaced to other cables and can only be approached from one direction.
Accordingly, it is general object of the present invention to provide a new and improved clamp mechanism and housing for circuit monitoring devices.
It is a more specific object of the present invention to provide a clamp mechanism and housing for installing a circuit condition monitoring device on the cable of a power distribution system which requires the use of one hand during installation.
It is a further object of the present invention to provide a clamp mechanism for clamping a circuit condition monitoring device to the cable of a power distribution system wherein the cable has a range of diameters.
It is a still further object of the present invention to provide a clamp mechanism for application and removal thereof to the cable of a power distribution system by the manipulation of a live line tool.
These and other objects, features and advantages of the present invention will be clearly understood through a consideration of the following detail description.